Only do ensurePort for XMPP transport

If we always do this the address gets mangled, breaking the transport
selection.

client.go

@@ -133,8 +133,6 @@ func NewClient(config Config, r *Router) (c *Client, err error) {
 			}
 		}
 	}
-	config.Address = ensurePort(config.Address, 5222)
-
 	c = new(Client)
 	c.config = config
 	c.router = r

transport.go

@@ -39,5 +39,7 @@ func NewTransport(config TransportConfiguration) Transport {
 	if strings.HasPrefix(config.Address, "ws:") || strings.HasPrefix(config.Address, "wss:") {
 		return &WebsocketTransport{Config: config}
 	}
+
+	config.Address = ensurePort(config.Address, 5222)
 	return &XMPPTransport{Config: config}
 }